Don't coerce to numeric when coercing IDate to Date (#6940)

Author: MichaelChirico

NEWS.md

@@ -10,6 +10,8 @@
 
 3. `print.data.table()` now shows column classes at the bottom of large tables when `class=TRUE` and `col.names="auto"` (default) for tables with more than 20 rows, [#6902](https://github.com/Rdatatable/data.table/issues/6902). This follows the same behavior as column names at the bottom, making it easier to see column types for large tables without scrolling back to the top. Thanks to @TimTaylor for the suggestion and @Mukulyadav2004 for the PR.
 
+4. `as.Date()` method for `IDate` no longer coerces to `double` [#6922](https://github.com/Rdatatable/data.table/issues/6922). Thanks @MichaelChirico for the report and PR. The only effect should be on overly-strict tests that assert `Date` objects have `double` storage, which is not in general true, especially from R 4.5.0.
+
 ## BUG FIXES
 
 1. Custom binary operators from the `lubridate` package now work with objects of class `IDate` as with a `Date` subclass, [#6839](https://github.com/Rdatatable/data.table/issues/6839). Thanks @emallickhossain for the report and @aitap for the fix.

R/IDateTime.R

@@ -46,7 +46,6 @@ as.IDate.POSIXct = function(x, tz = attr(x, "tzone", exact=TRUE), ...) {
 as.IDate.IDate = function(x, ...) x
 
 as.Date.IDate = function(x, ...) {
-  x = as.numeric(x)
   class(x) = "Date"
   x
 }